Madonna With Child and Two Angels, Filippo Lippi (c1465)

Artist: Fra Filippo Lippi's life and art are pitched between religion and sensuality, piety and a Renaissance passion for this world. Born poor in 1406 in the district of the Carmine convent in Florence, he was placed there as a child. He chafed against his presumed vocation. Luckily, he had powerful protectors: the Medici, for whom he painted his Annunciation (probably 1450s), now in the National Gallery. Lippi's biographer Vasari claims that Cosimo de' Medici loved Lippi despite his antics, and saw his fiery nature as typical of "rare minds".

Subject: Lippi was chaplain to a convent in Prato, near Florence, where, says Vasari, he was painting an altarpiece for the nuns of St Margherita. There he saw the "beautiful and graceful" Lucrezia Buti, a novice. He persuaded the nuns to let him paint her as Our Lady, then persuaded Lucrezia to run away with him. The nuns were shamed, Lucrezia's father "never smiled again" - but she stayed with Filippo.

There is documentary confirmation of the tale - Lippi was denounced to Florence's office of the monasteries and of the night for having Buti, her sister and five other nuns living with him between 1456 and 1458. The friar and nun had a son and, later, a daughter.

The Virgin Mary in this most delicate and earthy of Florentine religious paintings has traditionally been identified as Lucrezia. Certainly, the same model poses as Mary in his circular, beautiful, Madonna and Child With the Birth of the Virgin and The Meeting of Joachim and Anna (c1452 or mid to late 1460s) in the Pitti Palace, Florence. These two paintings stand out among Lippi's works for the emotionally involved representation of a Madonna who seems unequivocally a real woman.

Distinguishing features: This Virgin's secular beauty is undeniable; she wears a huge pearl over her finely coiffured hair and a string of pearls receding in a striking triangle from her high forehead. Her sculpted face, the shadows playing on her cheek, her bowed nose and strong lips - all is crisply yet tenderly seen.

She sits on an ornate piece of furniture in a grey stone window through which we see cultivated fields, soaring rocks, a distant city. This is crucial to the painting's intimacy; it brings the Madonna forward. Her shadow is on the frame in a painting lit from the right - another physical, as opposed to spiritual detail. She is in front of it, like an actor at the front of a stage.

She inspires passionate filial devotion in Christ, who is lifted up on the shoulders of two angels. The angel in the foreground is the painting's riskiest figure. He doesn't seem to be playing his part at all; he seems to be a real child, forgetting his pose, looking back at the painter, laughing.

This is one of the most beautiful paintings of the Florentine Renaissance, a daring example of the humanising of religion that goes back to Giotto and, intellectually, to St Francis of Assisi. Just as St Francis used humble imagery to make Christianity accessible, Renaissance painters made the relation between Mary and child that of a real mother and baby. Here, the Madonna is a beauty to whom Christ and Lippi are in thrall.

Inspirations and influences: Just as it's tempting to identify the Madonna as Lucrezia, so the laughing angel has traditionally been seen as a portrait of their son, Filippino. He also became a painter, creating some of the greatest Renaissance grotesques in the Strozzi Chapel frescoes at Santa Maria Novella, Florence.